Sierra Lumber Company produces lumber. The company has two grades of lumber at the split-off point, A and B. Grade A sells for $4 per board foot and Grade B sells for $2 per board foot. This lumber is suitable for framing and most exterior work but not for the interior of buildings. Either grade can be further processed to make it suitable for interior work at a cost of $1.20 per board foot. After this further processing, the firm can sell Grade A lumber for $5.50 per board foot and Grade B for $3.00 per board foot. Would you recommend the company sell the lumber at the split-off point or process it further to make it suitable for interior work? Explain and give supporting computations.